Research Journal of Applied Sciences, Engineering and Technology 4(12): 1755-1761, 2012
ISSN: 2040-7467
© Maxwell Scientific Organization, 2012
Submitted: January 16, 2012
Accepted: February 09, 2012
Published: June 15, 2012
Characterization of Physical and Mechanical Properties of Branch, Stem
and Root Wood of Iroko and Emire Tropical Trees
1
M. Amoah, 1J. Appiah-Yeboahand 2R. Okai
Faculty of Technical and Vocational Education, University of Education, Winneba, Ghana
2
Rector, Koforidua Polytechnic, Ghana
1
Abstract: This study investigated the physical and mechanical properties of branch, stem and root wood of
iroko (Milicia excelsa) and emire (Terminalia ivorensis). The basic density, MOE and MOR were determined
in accordance with BS 373:1957. Fifty samples from the wood types of each species were used for each test.
The study showed that the root wood of iroko and emire exhibited the highest basic density of 760 and 620
kg/m3, respectively, while the basic densities of the branch and stem wood of emire (537 kg/m3) were
comparable. The differences in the MOE values among the wood types of iroko and emire were found to be
statistically insignificant. The MOR value of the branch wood of emire (73 MPa) was found to be significantly
higher than that of the stem wood (71 MPa). However, there was no significant difference between the MOR
values of the branch and stem wood of iroko (67 MPa). Basic density of all wood types was found to be a good
predictor of MOE in static. With exception of the root wood of emire, significant but low correlations were
found for the regression relationships between MOE and MOR. For the emire stem wood, MOE explained
about 41% of the variation in the MOR of that wood type. The study concludes that it is possible to substitute
the branch and root wood of iroko and emire for stem wood in many applications.
Key words: Basic density, compression parallel to grain, density, modulus of elasticity, modulus of rupture,
utilization
INTRODUCTION
The forest situation in Africa poses enormous
challenges to its economic development agenda. The total
forests area of Africa is 635 million hectares and this
accounts for 21.4% of its land area (FAO, 2009). This
forest area represents only 16% of the global forest area.
Depletion of the Africa’s forests is well documented.
According to FAO (2009), between 2000 and 2005, 4
million ha of forests were lost annually in Africa. The
growing demand for fuelwood and rapid urbanizations
coupled with increasing agriculture will exacerbate the
forest situation in Africa (FAO, 2009).
The future of the timber industry in Ghana is even
gloomier. The total forest area of Ghana stands at 5.5
million ha representing about 24% of the total land area.
Over the years, the country’s forest area has shrunk
substantially. According to FAO (2009), the annual rate
of decline of the forest area of Ghana stood at 135,000 ha
for the period between 1990 and 2000 and 115,000 ha
from 2000 and 2005. Between 1990 and 2005, the forest
area of Ghana experienced an annual decline rate of 2%.
What is most worrying is the eminent extinction of most
of the commercial timber species. In the estimation of the
International Institute for Environment and Development
(IIED), the supplies of the traditional timber species such
as edinam (Entandrophragma angolensis), sapele
(Entandrophragma cylindricum), iroko (Milicia excelsa)
and emire (Terminalia ivorensis) could fall by 50% within
five years (Acquah and Whyte, 1998). In the face of the
scarcity of timber resource, logging residues have been
reported to be relatively high in Ghana. A study
conducted by Amoah (2008) in three ecological zones of
Ghana indicated that about 25% of merchantable wood in
the form of branches and stems was left as residues during
logging operations.
On account of decreasing raw material supply and the
environmental concerns about the depletion of the tropical
forests, industrial utilization of branches and roots has
been a subject of interest to researchers and industry. In
the estimation of Hilton (2001), branch wood represents
25-30% of the total wood volume. Even though branch
wood represents a secondary resource its potential
utilization has less been investigated. Increasing the added
value of branches indicates finding alternative uses other
than firewood or particleboard for wood-based panels
(Gurua et al., 2008). The commercial utilization of wood
residues in Ghana has been investigated by several
researchers (Amoah, 2008; Amoah and Becker, 2009;
Okai et al., 2004). The utilization of branches and roots
Corresponding Author: M. Amoah, Faculty of Technical and Vocational Education, University of Education, Winneba, Ghana
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Res. J. Appl. Sci. Eng. Technol., 4(12): 1755-1761, 2012
may depend on their dimensions, physical and mechanical
properties. Amoah and Becker (2009) conducted a study
on the assessment of logging efficiency at three logging
sites in Ghana and found that the Small-End Diameter
(SED) of the branch stems and main stem left at the
logging sites averaged between 31 and 60 cm while the
average length of the residues varied from 3.0 to 8.5 m.
The diameter and length of the branch wood of iroko
(Milicia excelsa) for example, was found to be about 51
cm and 6 m respectively. The dimensions of these
residues suggest that they could be used to manufacture a
wide range of products, including furniture parts, tongue
and groove and door frames.
Branch wood could potentially serve as a substitute
for stem wood if its physical and mechanical properties
are known and understood (Cionca et al., 2006).
Knowledge of the mechanical properties of wood allows
for better optimization and for minimal use of raw
material (Van de Kuilen and Blass, 2005). The study of
the mechanical properties of timber species is therefore
indispensable if the species are to be selected and used in
the various domains of engineering. The knowledge of the
mechanical properties of timber species allows for their
characterization of their behavior under different
applications (Santos and Pinho, 2004).
The physical and mechanical properties of root and
branch wood of tropical trees in Ghana have been less
investigated. Okai (2004) investigated the physical and
mechanical properties of branches and stems of emire
(Terminalia Ivorensis) and asanfina (Anigeria robusta).
The author reported that the branches of the two species
had higher densities and MORs than their corresponding
stems. In this study, the variation in the physical and
mechanical properties of branches, stems and roots of two
tropical tree species, emire (Terminalia Ivorensis) and
iroko (Milicia excelsa) were investigated. The properties
of wood investigated were density at 12%MC, basic
density, Modulus of Elasticity (MOE) and Modulus of
Rupture (MOR) and compression strength parallel to the
grain. The two questions raised in this study were:
Fig. 1: Rootwood of iroko being extracted for the study
between the months of March and September. Two
hardwood timber species, iroko (Milicia exlcesa) and
emire (Terminalia ivorensis) were selected for the study.
The selection of these timber species was based on their
high economic value and their eminent extinction
(Acquah and Whyte, 1998). Therefore the total utilization
of their branch and root wood could reduce their felling
rates. Three straight trunk each of iroko and emire and
representing the average diameters of the two timber
species at breast height were sampled. Straight stem,
branch and root pieces were randomly taken from the
sampled trees of iroko and emire. The root pieces were
obtained by digging a trench profile of 600mm wide and
1200mm deep parallel to the direction of the root (Fig. 1).
MATERIALS AND METHODS
Preparation of test samples: The preparations of the test
specimen were based on BS 373:1957 ‘Method of Testing
Small Clear Specimens of Timber’. Bolts of stem, branch
and root wood of iroko and emire were sawn into boards.
The boards were then planed and carefully examined for
visible defects. The boards from each of the timber
species and wood type were given identification numbers.
From these boards, test specimens were prepared for the
determination of basic density, static bending (Modulus of
Elasticity, Modulus of Rupture) and compression parallel
to the grain.
The study was carried out in the Tinte Bepo forest
reserve located in the semi-deciduous forest type (latitude
7º5!N and longitude 2º2!W) in the Ashanti Region of
Ghana. Data were collected from the reserve in 2009
Physical and mechanical tests: The tests were carried
out at the Structural Testing Laboratory at the Kwame
Nkrumah University of Science and Technology
(KNUST)-Civil Engineering Department, under the
C
C
How comparable are the density, MOE and MOR
values of branch, stem and root of the same species?
Since there is a paradigm shift to the use of NonDestructive Test (NDT) to estimate the mechanical
properties of wood (Lei et al., 2005), the second
question was whether it is possible to predict
modules of rupture from modules of elasticity?
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Res. J. Appl. Sci. Eng. Technol., 4(12): 1755-1761, 2012
guidance of competent technicians. The Universal Testing
Machine was used for the strength tests. Fifty specimens
from the wood types of each species were used for each
test.
Basic density: The density of the timber species which
was determined according to ASTM Standard D 143-52,
was based on the volumes of the specimens at the time of
the test and their weights when oven-dried. The test
specimens were 300 mm in length with a cross-section of
50*50 mm.
Static bending: The strength properties determined from
the static bending test were Modulus of Elasticity (MOE)
and Modulus of Rupture ((MOR). The test specimens
were 300 mm long, with a 20*20 mm cross section as
recommended in BS 373 (1957) for clear specimens
(Gurua et al., 2008; The Princes Risborough Laboratory
of the Building Research Establishment, 1974). Fifty
specimens were prepared for each set of test variables.
The actual specimen dimensions were measured with
digital calipers calibrated with a 25-mm ± 0 :m slide. The
specimens were stored in a room for three weeks and
equilibrated to approximately 12% MC. The actual
moisture content was determined after testing by using the
moisture meter method and validated by oven-dry
method. The mean value for each set of the specimens
was recorded. The MOE of the specimens was calculated
by the following equation (Pashin and de Zeeuw, 1980):
MOE =
l3
4bd 3
x
w
x
(l)
where l is the length of span (mm), w is the imposed load
(N), b width of specimen (mm) and thickness of specimen
(mm) and )x deflection at mid-span. The term )w / )x is
the gradient of the elastic region of the load-deflection
graph. The MOR of the specimens was also calculated by
the following equation:
MOR =
3 wl
4bd 3
!
(2)
where w is load at failure.
Compression strength parallel to the grain: The
compression strength parallel to the grain test was
performed according to BS; 373 (1957). 300*50*50 mm
specimens were employed and the test was performed on
a compression universal machine. As in the case of the
static bending test, the specimens were stored in a room
for three weeks to allow the moisture content to
equilibrate to about 12%. The actual moisture content of
the specimens was determined by electrical moisture
meter after testing. Specimen dimensions were measured
to the nearest 0.001 mm the dimension before the testing.
The compression strength parallel to the grain was
calculated by the following equation (Pashin and de
Zeeuw, 1980):

cpl

W max
F
where Fcpl is the compression strength (MPa), Wmas is the
maximum load at the break points (N) and F is area of
cross-section of a specimen on which force was applied.
Data analysis: The data were analyzed using descriptive
statistics, one-Way Analysis of Variance (ANOVA).
RESULTS
Density (at 12% MC) of Milicia excelsa (iroko) and
Terminalia ivorensis (emire) wood types: The statistical
summary of the densities of the species is shown in
Table 1. Among the wood types of iroko, the root wood
had the highest average density (760 kg/m3), ranging
between 694 and 813 kg/m3. Branch wood had the lowest
average density (751 kg/m3), varying between 694 and
808 kg/m3. Statistical analysis (One-Way ANOVA)
indicated, however, that the differences among the
densities of wood types of iroko were not statistically
significant (p-value = 0.134) (Table 1). In the case of
emire, the root wood had the highest average density of
(620 kg/m3) ranging from 597 to 693 kg/m3, while the
stem wood had the lowest (577 kg/m3), also varying
between 568 and 609 kg/m3 .The average density of the
branch wood was 611 kg/m3, with the minimum and
maximum values of 569 and 624 kg/m3, respectively. The
One-Way ANOVA test indicated that the differences
among the densities of the wood types of emire were
statistically significant at the 5% level (Table 1).
Basic density of Milicia excelsa (iroko) and Terminalia
ivorensis (emire) wood types: Table 1 contains the
statistical summary of the basic density values of the
wood types of the two timber species. Among the wood
types of iroko, the root wood recorded the highest average
basic density (712 kg/m3), while the branch wood
recorded the lowest (625 kg/m3). The basic density of the
root wood of iroko ranged from 628 to 743 kg/m3,, while
those of the stem and branch wood varied between 625
and 637, 604 and 635 kg/m3, respectively. The average
basic density values of the root, stem and branch wood of
iroko were respectively, 94, 85 and 83%, respectively of
their corresponding density values at 12% MC. As found
for iroko, the root wood of emire had the highest average
basic density (601 kg/m3), varying between 534 and 640
kg/m3. Both the stem and branch wood types of emire had
the average basic density of 534 kg/m3 and ranged from
496 to 597 kg/m3. The One-Way ANOVA test showed
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Res. J. Appl. Sci. Eng. Technol., 4(12): 1755-1761, 2012
Table 1: statistical summary of density at 12% MC and basic density of timber species studied
Density (Kg/m3) at 12% m.c
Basic density (Kg/m3)
---------------------------------------------------------------------------------------------------------------------------Species
Statistic
Branch
Stem
Root
p-value
Branch
Stem
Root
p-value
Iroko
Mean
751
752
760
0.134
625ab
637ac
712bc
0.001
Standard deviation
22.68
22.76
25.59
7.67
4.62
22.90
Coefficient of
3.0
3.0
3.4
1.2
0.7
3.2
variation (%)
Minimum value
694
696
694
604
625
628
Maximum value
808
800
813
635
637
743
Emire
Mean
611ab
577ac
620bc
0.001
537a
537b
601ab
0.001
Standard deviation
12.19
7.67
13.64
19.03
19.03
23.90
Coefficient of
2
1.3
2.2
3.5
3.5
4.0
variation (%)
Minimum value
569
568
597
496
496
534
Maximum value
624
609
693
597
597
640
Values sharing the same letter are significantly different at 0.05 using Tukey Test Post hoc
Table 2: Experimental results for MOE
MOE of iroko wood types (GPa)
MOE of emire wood types (GPa)
-------------------------------------------------------------------------------------------------------------------------------------Statistic
Branch
Stem
Root
p-value
Branch
Stem
Root
p-value
Iroko
Emire
Mean
12.9
13.2
12.9
0.612
7.6
7.6
7.7
0.663
Standard deviation
1.27
1.33
1.23
0.56
0.56
0.64
Coefficient of variation (%) 9.7
10.1
9.5
7.4
7.4
8.3
Minimum value
11.2
11.2
10.9
5.5
6.05
.6
Maximum value
15.8
15.8
15.8
9.1
8.8
9.0
Values sharing the same letter are significantly different at 0.05 using Tukey Test Post hoc
that the difference between the basic density values of the
root wood and the stem and branch wood was significant
at the 5% probability level (Table 1). The average basic
density values of the root, stem and branch wood of emire
were respectively, 97, 93 and 88%, respectively of their
corresponding density values at 12% MC.
Modulus of Elasticity (MOE): The MOE of the iroko
wood types varied from 12.9 to 13.2 GPa, with the stem
wood recording the highest (Table 2). The MOE of both
the branch and stem wood of iroko ranged between 11.2
to 15.8 GPa, while that of the root wood varied from 10.9
to 15.8 GPa. The average MOE of the branch and root
wood was about 98% of the stem wood. The ANOVA test
showed that the differences of the MOE among the wood
types of iroko were not significant at the 5% level. The
MOE of the wood types of emire ranged from 7.6 to 7.7
GPa. The MOE of emire root wood (7.7 GPa) was slightly
higher than those of the branch, stem and root wood (7.6
GPa) (Table 2). The MOE values of the branch, stem and
root wood ranged from 5.5 to 9.1, 6.0 to 8.8 and 5.6 to 9.0
GPa, respectively. As found in the case of iroko, the OneWay ANOVA test did not show any significant difference
among the MOE values of the wood types of emire.
Bending strength (Modulus of rupture): The
experimental results of the bending strength (MOR) and
compression parallel to the grain of the branch, stem and
root wood of iroko and emire are summarized in Table 3.
Among the wood types of iroko, the MOR of the root
wood (67 MPa) was higher than those of the branch and
stem wood (64 MPa). The MOR of the root wood varied
between 57 and 75 MPa, while those of the branch and
stem wood ranged from 53 to 71 and 57 and 71 MPa,
respectively. The One-Way ANOVA test revealed that the
MOR of the root wood of iroko was significantly higher
than those of the branch and stem wood (Table 3).
As found for iroko, among the wood types of emire,
the root wood had the highest MOR while the stem wood
had the lowest. The MOR of the root wood was 74 MPa,
varying between 53 and 85 MPa. The MOR of the branch
wood averaged 73 MPa, also ranging from 66 to 85 MPa,
while that of the stem wood was 71 MPa, varying
between 62 and 75 MPa. The One-Way ANOVA test
showed that the average MOR values of the root wood
and branch wood were significantly higher than that of the
stem wood. However, no significant difference was found
between those of the root and the branch wood at 5%
level of probability (Table 3).
Compression parallel to the grain: The root wood of
iroko was found to exhibit the highest average
compression strength, while the branch wood exhibited
the lowest (Table 3). The average compression strength of
the root wood of iroko was 57 MPa, ranging between 40
and 64 MPa, while the stem wood had average
compression strength of 46 MPa varies from 42 to 48
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Res. J. Appl. Sci. Eng. Technol., 4(12): 1755-1761, 2012
Table 3: Experimental results for bending and compression strength of the wood types of iroko and emire
Bending strength (MOR) Mpa
Compression parallel to the grain (MPa)
------------------------------------------------------------------------------------------------------------Species
Statistic
Branch
Stem
Root
p-value
Branch
Stem
Root
p-value
Iroko
Mean
64a
64b
67ab
0.012
44ab
46ac5
7bc
0.001
Standard deviation
4.55
4.25
3.90
2.90
0.96
6.22
Coefficient of variation (%) 7.1
6.6
5.8
6.5
2.1
10.9
Minimum value
53
57
57
27
42
40
Maximum value
71
71
75
47
48
64
Emire
Mean
73a
71ab
74b
0.008
47a
46ab
47b
0.008
Standard deviation
3.95
3.11
5.00
1.98
2.15
1.79
Coefficient of variation
5.4
4.4
6.8
4.2
4.7
3.7
Minimum value
66
62
53
42
40
47
Maximum value
85
75
85
50
48
49
Values sharing the same letter are significantly different at 0.05 using Tukey Test Post hoc
Table 4: Prediction equations for estimating MOR from MOE
Species
Emire
Iroko
Wood type
Branch
Stem
Root
Branch
Stem
Root
Regression equation
MOR = 3.168MOE+48.8
MOR = 3.556MOE+44.4
MOR = 1.818MOE+60.0
MOR = 2.094MOE+36.6
MOR = 1.58MOE+44.2
MOR = 1.14MOE+52.2
2
r
0.451
0.643
0.232
0.584
0.494
0.360
R
0.204
0.414
0.054
0.342
0.244
0.129
MPa. The compression strength of the branch wood
averaged 44 MPa with the minimum and maximum values
of 27 and 47MPa, respectively. The ANOVA test showed
that there were significant differences among the
compression strength values of the wood types of iroko
(Table 3). Among the wood types of emire, the strength
values of the root and branch wood were higher than that
of the stem wood (Table 3). The compression strength of
the root wood averaged 47 MPa and ranged from 47 to 49
MPa, while that of the branch also averaged 47 MPa and
varied between 42 and 50 MPa. The stem wood had an
average compression strength of 46 MPa, varying
between 40 and 48 MPa. The One-Way ANOVA test
showed that the differences among the compression
strength values of the wood types were significant at the
5%level (Table 3).
Prediction equations for estimating MOR from MOE:
The MOE was used to predict the MOR of the wood types
of iroko and emire. Table 4 contains the prediction
equations. Statistical analysis indicated that, with the
exception of emire root, the relationships between MOR
and MOE for the rest of the iroko and emire wood types
were significant at the 99% confidence level (Table 4),
even though the correlations were weak. The r-values
ranged from 0.45 to 0.64 for emire wood types and 0.36
to 0.58 for iroko wood types.
DISCUSSION
Density at 12% MC of iroko and emire wood types:
Because, in general, strength of wood increases with
95% C.I
--------------------------Upper
Lower
1.349
4.986
2.328
4.785
-0.397
4.032
1.252
2.937
0.764
2.396
0.281
1.993
t-test
3.502
5.82
1.651
4.999
3.896
2.670
Sig. (2-tailed)
0.001
10.001
0.105
0.001
0.001
0.001
increasing density (Tsoumis, 1968), the determination of
densities of the branch, stem and root wood of the two
species investigated in this study was instructive. The
average density values of the stem wood of iroko (752
kg/m3) and emire (577 kg/m3) found in this study were
respectively about 16 and 5% higher than the values
reported elsewhere (Timber Expert Development Board,
1994). The density of the stem wood of iroko found in this
study was in the range reported by Wu et al. (2009). The
author reported that a SilveiScan density of iroko was 786
kg/m3 which is 4.5% higher than the value reported in this
study.
The study showed that the root wood of both iroko
and emire had higher average density values than their
corresponding values for the branch and stem wood. This
finding is consistent with the study by Peterson et al.
(2007). The authors investigated the juvenile wood in the
branches and roots of Douglas-fir and reported that the
roots had higher density wood than the stem. Higher
density of branch wood of emire found in this study
corroborated the findings of the previous studies (Fegal,
1941; Kollman and Côté, 1968; Tsoumis, 1968). Okai
(2003) investigated the physical and mechanical
properties of the branch and stem wood of emire
(Terminalia ivorensis) and asanfina (Aningeria robusta)
and reported that for both species, the branch wood has
higher densities than the corresponding stem wood.
Branch wood exhibits higher density possibly because it
is characterized by higher percentage in the volume of
fibers (Hakkila, 1989). While the density of branch wood
of emire was statistically significantly higher than that of
the stem wood, no significant difference was found
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Res. J. Appl. Sci. Eng. Technol., 4(12): 1755-1761, 2012
between the densities of the branch and stem wood of
iroko. The difference between stem and branch wood
densities appears to vary among species rather
unpredictably (Manwiller, 1974; Hakkila, 1989). Gurua
et al. (2008) found that the densities of the branch wood
of beech and maple were higher than the corresponding
densities of their stem wood. The authors reported,
however, that the stem wood density of Scot pine was
higher than that of the branch wood. Higher densities of
stem wood than the branch wood of softwoods have been
reported in the literature (Brunden, 1964; Philips et al.,
1976).
Basic density of the wood types of iroko and emire:
Basic density is used as a measure of wood quality and a
predictor of end-use properties (Lindstrom, 1996). The
basic densities of the branch stem and root wood of iroko
and emire were therefore compared to allow for their end
use potential. Cheng et al. (1992) reported that the basic
densities of iroko stem wood ranged between 620 and 720
Kg/m3. In this study the basic density of the stem wood of
iroko varied from 625 to 637 Kg/m3 which were in the
range reported by Cheng et al. (1992). The basic densities
of the root wood of iroko and emire were found to be
higher than those of the branch and stem wood and the
differences were statistically significant at 5% or higher.
The basic densities of the root wood of iroko and emire
were found to be higher than that of the branch wood and
the difference was statistically significant at the 5% level.
The basic densities of the root stem and branch wood of
iroko were 94, 84 and 83%, respectively of their
corresponding densities at 12%, MC. In the case of emire,
the basic densities of the root stem and branch wood were
97, 93 and 88%, respectively of their corresponding
density values at 12% MC. This showed that the root
wood of both iroko and emire exhibited the lowest
decreased in density from 12% MC to oven-dry weight.
Bending strength of the wood types of iroko and
emire: The average MOE of iroko wood types found in
this study ranged from 12.3 GPa for the branch and root
wood to 13.2 GPa for the stem wood. The MOE values
for the wood types of emire also varied from 7.6 to 7.7
GPa. The differences in the average MOE values among
the wood types of iroko and emire were however found to
be statistically insignificant (Table 2). The MOE of the
branch wood of iroko was about 98% of that of the iroko
stem, while in the case of emire no difference was found
between them. The MOE value for the stem wood (13.2
GPa) found in this study is comparable to the value
reported by CIRAD (2009) and falls between values
obtained by Cheng et al. (1992), 9.30-9.40 GPa and the
SiliviScan value (16.1 GPa) reported by Wu et al. (2009).
Contrary to expectation, the higher densities of the root
wood of iroko and emire did not translate into
higher MOE.
Emire wood types exhibited higher MOR values than
the iroko wood types. The MOR values for the branch,
stem and root wood of iroko were respectively 88, 90 and
91%, respectively of the corresponding values of the
emire wood types. The MOR values obtained in this study
for iroko varied from 64 MPa for the branch and stem
wood to 67 MPa for the root wood. The MOR for the
branch and stem wood of iroko was about 96% of that of
the root wood of iroko. In the case of emire, the MOR
ranged between 71 MPa for the stem wood and 74 MPa
for the root wood. The MOR for the branch wood of
emire was found to be 3% higher than that of the stem
wood of emire. This difference was found to be
statistically significant at the 5% probability level.
Prediction equations for estimating MOR from MOE:
The regression relationship between MOE and MOR is
important because it represents a non-destructive
prediction of MOR of wood based on the known value of
MOE which can be obtained without damaging the wood
material (Kollman and Côté, 1968; Lei et al., 2005). With
the exception of root wood of emire, significant but low
correlations were found for the regression relationships
between MOE and MOR of the other wood types of emire
and iroko. For the emire stem wood, MOE explained
about 41% of the variation in the MOR of the wood types.
The r2 values reported in this study appear similar to those
reported elsewhere for tropical hardwoods (Green and
Rosales, 1996).
CONCLUSION
In this study, the potential utilization of branch and
root wood of iroko and emire was explored by
characterizing their physical and mechanical properties.
In general, the root wood of both species exhibited higher
density. MOE, MOR and compression parallel to the
grain values of root wood were higher than those of the
branch and stem wood. The physical and mechanical
properties of branch and stem wood of both species
appear comparable. The MOE of the wood types of both
species increased with increasing wood density at 12%
MC. Significant but low correlations were found for the
regression relationships between MOE and MOR of the
wood types of iroko and emire. The study concludes that
it is possible to use branch and root wood of iroko and
emire for many engineering and structural applications.
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